The field of the disclosure relates generally to structural health monitoring, and more particularly relates to methods and systems for aircraft structural health monitoring.
Some structural health monitoring (SHM) systems can be used to monitor an aircraft structure. One example SHM system is formed using an array of piezoelectric transducers (PZTs) bonded to a structure. Each PZT, acting one at a time, broadcasts a vibration signal and all other PZTs bonded to the structure record the signal as received at their location. Such an interrogation is performed when the structure is at a known, good state and the received signals are recorded and saved as reference signals. When, at some future time, the structure is interrogated again, the newly received signals are compared to the reference signals. Any differences found between the reference signals and the new signals may indicate damage to the structure and/or correlate to the magnitude of damage to the structure. The differences between the reference signals and the new signals are generally reduced to a single number called a Damage Index (DI), with larger values indicating more damage.
Some known systems use broadband excitation and use differences in a signal transfer function to calculate a DI. Damage is localized by noting the location of the actuator with the highest magnitude DI, identifying the three adjacent transducers with the greatest sum of DIs, and then using center of mass equations to locate damage. Finally, the system produces a qualitative, but not quantitative, characterization of damage.